Ralt RT-3 -82 setup

[Henrik]

Hello
I´m helping a friend with a pre season setup of a Ralt RT-3 1982 The current front springs seems way to soft for a wing car and wonder if anyone have a clue what to start with setup wise.

The car is in flat bottom / non ground effect setup with original wings.
Tyres are Avon 7.5/21x13 and 9.2/22x13 Avon Crossply.
At the moment there is 250lb/in front springs with a lot of bump rubber
At rear there is something "hard" that´s been cut......
Shocks are Bilsteins, probably from the period
Front rocker ratio is 0,81 (155/190 in/out)
Rear rocker ratio is 0,68 (125/185 in/out)
Minimum wehight is 455Kg
Minimum ground clearance is 40mm

Im looking for
spring rates
Camber
Toe
Ride height / rake

/Henrik

[Charles Warner]

Hej Henrik,

The car as pictured does not have 1982 side pods. You say it is in flat bottom configuration. Does this mean the tunnels have been covered with flat sheet?

Try front springs at 400, rear at 600. Rake should be set at .400" between front of tub and rear of tub. This is to provide for a level platform at approx 100 mph.

Front ride height: start at .500" at front of tub. This should NOT include the stock Ralt front skid plate which can efectively lower the clearance by .125". Rear determined by rake.

Camber: try 0 at the rear and start with .5 degree negative at the front.

Toe: .125" total IN at the rear and .250 total OUT at the front.

These are good safe initial settings that can be played with as your friend gets faster.

Hej do

[Henrik]

Hi,
The sidepods underside are flat exept for the last 30cm where they bend up slightly (5cm) to clear the rear lower control arm.
There is nothing under the engine
Would it benefit to have a sheet under the engine?
Should there be any venturi tunnels after the rear axle?

HH

[Charles Warner]

Hi,
The sidepods underside are flat exept for the last 30cm where they bend up slightly (5cm) to clear the rear lower control arm.
There is nothing under the engine
Would it benefit to have a sheet under the engine?
Should there be any venturi tunnels after the rear axle?

There should be a structural sheet under the engine from the rear of the tub to the front of the gearbox adaptor.

I would not worry about any sort of tunnels rear of the axles. That is an unknown area on these cars and would probably unbalance the aero effects that have already been compromised by the closing off of the tunnels.

[Aslak H H]

[quote=Henrik;206500]Hello
I´m helping a friend with a pre season setup of a Ralt RT-3 1982 The current front springs seems way to soft for a wing car and wonder if anyone have a clue what to start with setup wise.

The car is in flat bottom / non ground effect setup with original wings.
Tyres are Avon 7.5/21x13 and 9.2/22x13 Avon Crossply.
At the moment there is 250lb/in front springs with a lot of bump rubber
At rear there is something "hard" that´s been cut......
Shocks are Bilsteins, probably from the period
Front rocker ratio is 0,81 (155/190 in/out)
Rear rocker ratio is 0,68 (125/185 in/out)
Minimum wehight is 455Kg
Minimum ground clearance is 40mm

Im looking for
spring rates
Camber
Toe
Ride height / rake

/Henrik



Hi!
I am the lucky friend, who is getting help from Henrik with the Ralt F3 –82.
As Henrik wrote, the tyres are in front Avon 7.5/21x13 and rear 9.2/22x13 Avon Crossply.

Is crossply essential on this F3, or can radial be used optional?


Aslak

[Charles Warner]

The car was designed for cross-ply tires. There are no known suspension settings for radials. I don't even know if there is enough suspension adjustability to compensate. IMO stick with the cross-ply tires.

[Henrik]

Hi Charles,

You say 0.5" front ride height, The regulations stipulate 40mm (1,6") minmum ride height How would this effect camber settings as the suspension would be in an other part of the camber curve

Doesn´t 1/4" toe out at front seem a bit agressive, I have never used more than 2mm on my FF1600 (threaded Donlop crossplies)

I have ordered 4,5 and 600lb springs for it. as the lenght is the same front and rear we can play around a little.

Henrik

[Charles Warner]

Henrik,

The regs should specify a 40mil side pod skirt height, not the ride height of the tub.

I have no experience with treaded tires but a total of .250" toe out at the front is not what I would call aggressive. I have seen as much as .500".

[Henrik]

From the 1983 F3 regulations

8. Aerodynamic devices must comply with the rules relating to coachwork, and must be
firmly secured whilst the car is in motion. Under no circumstances can any part of the
bodywork or of the suspended part of the car be below a horizontal plane passing 1 cm
under the bottom of the drivers seat and at least 4 cm above the ground, the car being
in normal racing trim with the driver on board. In order to allow the scrutineers to
carry out this check a 10 mm diameter hole will be bored through the bottom of the
seat and the corresponding floor.

I see this as the monoqoque shold be at least 40mm of the ground.
http://www.classicformula.se/downloa...mente_1983.pdf
(Page 14-24 in english)

In the 1989 F3 regs it seams that the minimum ride height is gone
http://www.classicformula.se/downloa...reg%201989.pdf


The threaded tyres I refered to was related to the VD RF85 FF1600 that I drive. I have no experience with slicks so I just thought it was a bit much.

Henrik

[Charles Warner]

Henrik,

IMO that means any part of the suspension. Unless there was a tremendous change from the RT-3 to the RT-5 - and there could have ben - a 1/6" front ride height would be way too much. I'm sure there are people in the UK or Australia that have the proper specs. They could help you more.